A pneumatic tire having a tread pattern where a plurality of straight main grooves are circumferentially provided on a tread surface is known as disclosed in Japanese Patent Application Kokai publication No. Hei 7 (1995)-164829 and the like, for example.
However, although the pneumatic tire having a tread pattern as described above is excellent in water discharge capability, on the contrary, the pneumatic tire has suffered from a disadvantage that cavity noise is large.
In order to reduce a disadvantage of having cavity noise caused by the straight main grooves provided circumferentially as described above while maintaining an advantage of having excellent water discharge capability caused by the straight main grooves as much as possible, a plurality of tread patterns where main grooves having a V-shape are provided have been proposed.
However, the tread pattern where main grooves having a V-shape are provided does not necessarily have sufficient water discharge capability at a time when a vehicle travels in a straight direction for their widths. To overcome this problem, however, if the width is broadened in order to improve the water discharge capability, a footprint width will decrease, thereby leading to the reduction of cornering force which causes the operation stability to decrease.
Therefore, the capability level of the pneumatic tire in which main grooves having a V-shape are provided as described above does not always exceed the capability level of the pneumatic tire based on circumferential straight main grooves as described in the aforementioned Japanese Patent Application Kokai publication No. Hei 7 (1995)-164829.